Electronic mail (hereinafter e-mail) is generally used to transmit information to only a particular person. In this case, of course, both a transmitting device and a receiving device need to have e-mail software. Lately, most of PC (personal computer) purchasers make use of e-mail, so e-mail software is usually installed in a PC sold.
Meanwhile, TV products capable of connecting to a network have lately gone on sale. However, TVs may not be connected to networks as often as PCs. E-mailing with a TV set that a family often view together would be utilized less frequent than PCs. Thus, installing e-mail software in a TV set is impractical in terms of development cost in spite of having the capability of connecting to network.
It is possible that a TV set connected to a network accesses a server and requests a content delivery from the server, even though having no e-mail software. Patent Document 1 discloses a method for scheduling a download. This document states that this method measures the rate of downloading a test file, predicts time utile completion, sets a date and time to start a download so as to complete it at a user-desired time, and schedules the download, gaining agreement with the user. If the user does not agree, an alternative data and time to start a download is presented. Another method is also described in which download status is monitored and switching to another server takes place if the download is not likely to complete until a guaranteed end time. In Patent Document 2, a method is described in which a time zone in which a download is scheduled is divided and assigned to terminals, thus distributing loads.
Further, services like above-mentioned e-mail on TV are expected to increase in future. To accommodate this, a method for authentication signaling between a service receiving device and a service delivery server is described in Patent Document 3.    Patent Document 1: Japanese Laid-Open Patent Application No. 2003-67280    Patent Document 2: Japanese Laid-Open Patent Application No. 2004-185114    Patent Document 3: Japanese Laid-Open Patent Application No. 2001-350724